In recent years, silicone rubber has been finding increasing application in the electrical, electronics, office machine and automobile fields. A need has therefore emerged to develop parts of one-piece construction wherein a thermoplastic resin, thermosetting resin or a metal substrate is made to adhere strongly to silicone rubber.
Conventionally, to make a substrate adhere to silicone rubber in a one-piece construction, a primer containing a titanium ester was first applied to the substrate.
As said titanium ester was hydrolyzed by moisture in the air, however, the surface of the applied primer sometimes turned white under conditions of high temperature and high humidity, there was insufficient time for manipulation after applying the primer and the adhesive bond obtained was sometimes unstable.
Further, to obtain a large number of parts of one-piece construction, such as the large number of small components used in automobiles, the primer was sometimes applied to the substrates by dipping. If however several substrates were laid on top of each other, they sometimes stuck together after drying in a current of air and the overlapping parts turned white.
In Japanese Patent Kokoku (Published Examined Japanese Patent) No. 60-39101, a primer composition containing a vinyl acetate polymer is disclosed. This however can be used only where the silicone rubber which is made to the substrate is an addition curing type, and it also suffered from the disadvantage that the adhesive contact surface turned to yellow or brown at high temperature.
The inventors, after intensive efforts to resolve the above disadvantages, obtained excellent results using the silicone compound of given composition as a primer, and thereby arrived at the present invention.